1. Field of the Invention
The present invention relates to a load/unload unit and a control method thereof that are employed in hard disk drives (HDDs), and more particularly to a disk drive, a load/unload unit, and a control method thereof that have a load/unload mechanism by means of which a converter head for reading or writing data from or to a storage medium is loaded onto or unloaded from the storage medium.
2. Description of Related Art
In disk drives, a storage medium such as a magnetic disk is rotated. The rotation of this magnetic disk creates an air bearing that floats a head slider off the disk surface, the slider being mounted on a suspension assembly which constitutes the head arm of an actuator mechanism. With the floated head slider, data is written to or read from the disk. In a non-operative state where rotation of the disk is stopped, the head slider is landed on an evacuating zone, where no data is recorded. A disk drive such as this is referred to as a contact start stop type disk drive.
In the contact start stop type disk drive, there is a danger that the head slider will stick to the surface of a data area or it will be moved to the data area by shock and damage the disk surface. Therefore, with an object of avoiding such danger and enhancing reliability when not operated, a disk drive called a head load/unload type has been developed. A head load/unload type disk drive is equipped with a head load/unload mechanism. The head load/unload mechanism is equipped with a head hold mechanism, which includes a suspension assembly, a head arm and a component called a ramp block provided in the disk drive. When the disk drive is not operated, the head slider is unloaded to an evacuating position without touching the head slider to the disk surface by holding the suspension assembly on the ramp block. The suspension assembly is provided with a tab having a protruding portion. Also, the ramp block is formed with a ramp. The ramp block is disposed so that the ramp is positioned near the outer circumferential portion of the disk. The ramp surface is a combined flat surface having a first inclined surface, a second inclined surface, and a tab-holding flat surface. Note that a horizontal surface (top flat surface) may also be provided between the first inclined surface and the second inclined surface.
When the operation of the disk drive is stopped, the head load/unload mechanism unloads the head slider by rotating the head arm and placing the protruding portion of the tab of the suspension assembly on the tab-holding flat surface of the ramp. When unloading the head slider, the protruding portion of the tab first touches the first inclined surface, then slides on the first and second inclined surfaces, and arrives at the tab-holding flat surface. Also, when the operation of the disk drive is started, the head load/unload mechanism rotates the head arm and loads it over the disk surface being rotated. When loading the head slider, the protruding portion of the tab first slides on the tab-holding flat surface, the second inclined surface, and the first inclined surface and then leaves the first inclined surface.
In the case where power to the disk drive is turned off when the head arm is positioned over the disk surface, the head arm must be quickly evacuated to a predetermined outer circumferential position. However, power to the VCM spindle driver for rotating the head arm is also turned off, and consequently, in order to move the head arm to a predetermined evacuating position, there is only one way to use the back electromotive force of the spindle motor which drives the head arm to rotate on the spindle. That is, the head arm is unloaded by using the back electromotive force of the spindle motor immediately after power is turned off.
However, in the disk drive equipped with a head load/unload mechanism such as that described above, enhancements in reliability in unloading the head arm cannot be achieved, because the head arm is unloaded by the back electromotive force of the spindle motor generated immediately after power is turned off. Since the unloading operation is performed only once by using the back electromotive force, it is possible that the unloading operation will fail due to some situations such as external shock applied to the disk drive.
It therefore can be seen there is a need in the art to provide a disk drive, a load/unload mechanism and a control method thereof which is capable of reliably unloading a head arm when the power to the disk drive is turned off.